Polymerization of diacetone acrylamide by electrolysis



United States Patent 3,434,946 POLYMERIZATION 0F DIACETONE ACRYLAMIDE BY ELECTROLYSIS Raymond J. Ehrig, Silver Spring, and Frederick A. Kundell, Laurel, Md., assignors to W. R. Grace & Co., New York, N.Y., a corporation of Connecticut No Drawing. Filed Aug. 26, 1966, Ser. No. 575,259 Int. Cl. C08t 1/00 U.S. Cl. 204-72 3 Claims This invention relates to a coating process. More particularly, this invention relates to a method for coating a metal substrate with diacetone acrylamide polymer by an electrolysis process from a solution of the monomer.

Polymerization by electrolysis is well known in the art. However, the polymer formed by such a process is generally formed in solution and not as a coating on the electrode.

One object of the instant invention is to form a diacetone acrylamide polymer coating on the cathodic sur face of an electrolytic cell. Other objects will be obvious from a reading hereinafter.

In summary, the invention consists of a process for forming a polymeric coating on the cathodic surface of an electrolytic cell which comprises maintaining an electric potential between electrodes immersed in an aqueous electrolytic solution of diacetone acrylamide monomer in an inert atmosphere and recovering diacetone acrylamide polymer as a coating on the cathodic electrode.

Diacetone acdylamide, N(1,1-dimethyl 3-oxobutyl) acrylamide, has the formula:

0 H orn=orrd-N "o 1 t t a)2 CH;

CIIZ It has previously been known that diacetone acrylamide can be polymerized by using either free-radical or ionic chemical polymerization initiators.

In the instant invention the electrolytic apparatus can be any conventional electrolytic cell, e.g. the H or U type compartment cell or standard non-compare mented cell employing a source of DC voltage.

Any type of metallic electrodes are operable in the instant invention including Pt, Cd, Sn, Pb, V, Cr, Ti, W, Au, Bi, Ni, Al, Fe, Cu and Zn. It is obvious to one skilled in the art that care should be exercised in selecting the electrodes, especially when a high concentration of an acidic electrolyte is used, that the electrode is not dissolved therein.

Electrolytes which are operable in the instant invention include all soluble acids, bases and salts preferably acids and salts. The amount of electrolyte added is usually sufficient to give a 0.001 to 0.5 normal solution.

The amount of diacetone acrylamide monomer dissolved in the electrolytic aqueous bath is an amount sufficient to give a 0.001 to 10 molar solution, preferably 0.5 to 2.0 molar. Diacetone acrylamide monomer is instantly water soluble and is also soluble in most organic solvents. Although the diacetone acrylamide monomer is water soluble the homopolymer formed therefrom is water insoluble.

The coating process of the instant invention is usually performed at temperatures in the range 0 to 60, preferablv room temperature, i.e. 20 to 30 C.

The coating reaction can be carried out for varying periods of time ranging from 5 seconds to 5 hours.

During the electrolysis, a potential difference in the range 3-150 volts, preferably 20 to 30 volts is maintained between the electrodes (as determined by the silver perchlorate standard reference electrode).

It is also possible in practicing the instant invention to add a hydrogen-substituted peroxide to the aqueous electrolytic solution to increase the reaction rate and improve the binding of the polymer to the metal substrate cathode. Peroxides such as hydrogen peroxide, t-butyl hydroperoxide are operable in the instant invention. The peroxide, if employed, is added in an amount in the range 0.01 to 1.0% by volume of the aqueous electrolytic monomer solution.

The process of the instant invention is carried out at a current density in the range 0.1 to 20 milliamps/cm. preferably in the range 2-10 milliamps/cm.

The following examples are set out not to limit but to better understand the instant invention.

In all the examples, unless otherwise noted, the electrolytic cell used was a modified U-shaped tube with the anodic and cathodic compartments separated by a sintered glass disk. Both compartments were designed for maintaining an inert atmosphere, e.g. argon gas. Stirring in the compartments is controlled by the flow of the inert gas into the compartments. The electrodes support rods entered the cell through ground glass joints with a piece of tygon tubing placed on each support rod to regulate the height of the electrodes in the solution. Unless otherwise noted, the area of the cathode in the electrolytic solution was 25.8 cm. The cell was placed in a constant temperature bath and connected to a DC power supply. Unless otherwise noted the anode was platinum metal whereas various metals were used as the cathode as will be shown in the examples.

Example 1 To a modified U-shaped tube having an anode and cathode compartment separated by a sintered glass disk were charged 100 ml. aqueous solution, 1 M in diacetone acrylamide and 0.1 N in H to the cathode compartment and ml. aqueous solution, 0.1 N in H 80 to the anode compartment. 25.8 cm. of a weighed zinc cathode was immersed in the solution along with the same size platinum anode. Argon was bubbled through the solution to maintain an inert atmosphere in both compartments and a potential difference of 18 volts was maintained across the electrodes for 80 minutes. The voltage was shut off and the coated cathode removed and oven dried overnight. On reweighing, the cathode had a uniform coating of diacetone acrylamide polymer weighing 0.106 gm. An infrared spectrum of a sample of the coating showed it to be polyacetone acrylamide by the method set out in J. Polymer Sci. Part A, vol. 3, p. 1601 (1965). The polymer had a melting point in the range -120" C. and a specific gravity of 1.110 at 25 C Example 2 Example 1 was repeated except that the voltage was 22 volts. The polymer coating weighed 0.114 gm. On repeating Example 1 with a voltage of 36 volts, a polymer coating of 0.154 gm. was obtained. A voltage of 47 volts using the procedure of Example 1, resulted in a polymer coating of 0.243 gm.

The following examples show various conditions and concentrations in which the instant invention is o erable. In all examples, unless otherwise noted, a modified U- shaped tube maintained under an inert atmosphere, i.e. argon bubbled through the solution and having an anode and cathode compartment separated by a sintered glass disk was used along with a platinum anode. A 100 ml. electrolyte was charged to the cathode compartment and a 100 ml. aqueous solution containing electrolyte of the aqueous solution containing diacetone acrylamide and same normality was charged to the anode compartment.

TABLE I Monomer 1 Electrolyte 2 Voltage Current Electrolysis Weight Example No. concentration concentration (volts) density polymer 3 molar) (normality) (ma/cm?) Time (hr) Temp. (hr.) coating (mg) 0. 0.1 4 4 3 22 28 0. 5 0. 1 2 2 21 42 0. 5 0.1 17 4 1. 5 21 25 0.1 0.1 19 4 3 21 6 0. 5 0. 1 20 4 1 60 116 0. 5 0. l 20 4 0.3 21 12 0. 5 0.1 23 4 0.16 21 10 0. 5 0. 1 25 4 0.08 21 11 0. 5 0. 1 25 4 4 0 21 0. 5 0. 1 28 4 0.016 21 0. 5 0.1 28 4 2. 5 20.8 47 1.0 O. 1 28 4 1. 5 20.7 70 0. 5 0.1 31 (i 4 21 49 0. 5 0. 05 35 4 3 21 43 0. 5 0.1 8 3 21 57 1.0 0.0 75 1 20. 7 6 1.0 0.01 92 4 2 21 99 0. 1 0.001 129 1. 6 2. 5 20.9 76 0. 5 4 0.1 150 0. 8 0.82 21 41 1 Diacetone acrylamide used as monomer. 2 H280 used as electrolyte unless otherwise noted. 3 Polydiacetone acrylamide. 4 Acetic acid.

The following examples using the same modified U- 2 to maintain an Inert atmosphere 1n both compartments. a

shaped cell and procedure as those in Table I show various metals operable as the cathodic metal substrate in the present invention. In all examples platinum was used as the anode. The results are shown in Table II.

25.8 cm. of a weighed aluminum cathode was immersed into the solution along with the same size platinum anode. A potential difference of 40 volts was maintained across the electrodes and the electrolysis was carried out at room TABLE II Monomer Electrolyte 2 Voltage Current Electrolysis Polymer 3 Example No. Cathode concentration concentration (volts) density Wgt. time coating (molar) (normality) (Ina/em?) (hr.) (mg) l Diacetone acrylamide monomer. 2 H4804. 3 Polydiacetone acrylamide.

The following examples shows the operability of the instant invention when using a one compartment cell.

Example 31 To a 1000 ml. beaker was charged 400 ml. of a 0.5 molar diacetone acrylamide monomer solution along with 3 ml. of a 30% hydrogen peroxide solution and 7 ml. of 0.3 molar nn-methylenebisacrylamide (a crosslinking agent). The solution had a pH in the range 3-5. 25.8 cm? of a weighed tin cathode was immersed in the solution along with the same size platinum anode. Argon was bubbled through the solution to maintain an inert atmosphere and a potential difference of 7 volts was maintained across the electrodes. The electrolysis was carried out at room temperature for 20 minutes. The voltage was shut off and the coated cathode removed and oven dried. On reweighing, the cathode had a uniform coating of diacetone acrylamide polymer weighing 7 milligrams.

The following example shows the effect of using a hydrogen-substituted peroxide in the aqueous electrolytic solution.

Example 32 To a modified U-shaped tube having anode and cathode compartments separated by a sintered glass disk was charged to 100 ml. of a 1 molar diacetone acrylamide monomer aqueous solution along with 2.5 ml. of a 0.1 NH SO solution, 0.5 cc. of a 30% H 0 solution and 1 ml. of a 1 M NH Cl solution to cathodic compartment and 100 ml. of a 0.1 N H 80 solution to the anodic compartment. Argon was bubbled through the solution temperature. The weights of polymer coating on the cathode at various times are shown below:

Wgt. polymer coating (mg) Electrolysis time (min.)

Wgt. polymer Electrolysis time (min) coating (mg) A comparison of the runs in Example 32 shows that the addition of a hydrogen-substituted peroxide increases the polymerization reaction rate.

The coating process of the instant invention is useful in coating various metals to protect them from abrasion, corrosion and oxidation. Thus, it is possible by the instant invention to coat cans used in the food and beverage industries and other metal objects.

What is claimed is:

1. A process for forming a diacetone acrylamide polymer coating on the cathodic surface of an electrolytic cell which comprises maintaining an electric potential in the range 3-150 volts between electrodes immersed in an aqueous electrolytic solution of diacetone acrylamide monomer in an inert atmosphere and recovering diacetone acrylamide polymer as a coating on the cathodic electrode.

2. The process according to claim 1 wherein a hydrogen-substituted peroxide in an amount in the range 0.01 to 1.0% by volume of the aqueous electrolytic monomer solution is added to the aqueous electrolytic monomer solution.

3. The process according to claim 1 where it is performed at a temperature in the range 060 C.

References Cited UNITED STATES PATENTS 2,726,204 12/1955 Park 204-72 2,961,384 11/1960 McKinney et a1 204-59 6 3,140,276 7/1964 Forster 204-72 3,193,483 7/ 1965 Balzer 204-72 3,268,433 8/1966 Abere 204-181 3,330,745 7/1967 Smcts et al 204-72 FOREIGN PATENTS 566,274 11/ 1958 Canada. 1,210,186 2/1966 Germany.

OTHER REFERENCES Swann: Electra-Organic Chemical Preparations in Transactions of the Electrochemical Society, vol. LXIX, 1936, pp. 287-343, TP 250 A54, class 204, subclass 72.

15 JOHN H. MACK, Primary Examiner.

E. ZAGARELLA, JR., Assistant Examiner. 

1. A PROCESS FOR FORMING A DIACETONE ACRYLAMIDE POLYMER COATING ON THE CATHODIC SURFACE OF AN ELECTROLYTIC CELL WHICH COMPRISES MAINTAINING AN ELECTRIC POTENTIAL IN THE RANGE 3-150 VOLTS BETWEEN ELECTRODES IMMERSED IN AN AQUEOUS ELECTROLYTIC SOLUTION OF DIACTONE ACRYLAMIDE MONOMER IN AN INERT ATMOSPHERE AND RECOVERING DIACETONE ACRYLAMIDE POLYMER AS A COATING ON THE CATHODIC ELECTRODE.. 